N-hexane was a component of many degreasing products used by auto mechanics from 1990-2002; its use ceased when several mechanics were identified as having peripheral neuropathy. Exposure data suggested that these workers were exposed to levels of n-hexane less than half the Threshold Limit Value (TLV). Acetone, which has been shown in animal studies to potentiate the effects of n-hexane and increase persistence, was added to these products in 1997. This retrospective cohort study aims to investigate possible persistent neurologic, reproductive and ocular effects of n-hexane and acetone after cessation of exposure. The sample will be drawn from the cohort of mechanics employed in the Bay Area during 1990- 2002. The cohort of potentially exposed workers will be identified through union records (District 190 of the International Association of Machinists and Aerospace Workers). Data will be abstracted from the union records for all potentially eligible participants in the study. Based on knowledge of which employers used hexane-containing products, we will recruit a sample of 600 mechanics who had worked at automotive repair shops that had once used hexane-containing products and another 600 will be recruited from such shops that never used hexane-containing products. Participants will be administered a questionnaire to obtain histories of symptoms experienced and solvent use, as well as demographic data and potential confounder exposures. They will also be administered batteries of tests to assess peripheral nerve function and cognitive function, as well as a test of blue-yellow color discrimination. Urine samples will be collected for measurement of the gonadotropins FSH and LH. Animal evidence indicates that n-hexane may cause testicular atrophy, which would be reflected by raised urinary metabolite levels of the FSH. The questionnaire will also inquire about any fertility problems subjects may have experienced. Individual n- hexane and other solvent exposure profiles will be created on the basis of solvent use and employment histories combined with existing exposure measurements and historical product composition information. Statistical analysis of the data will investigate associations of exposure histories with symptomatology, clinical and laboratory test results, and time-to-pregnancy. These results may provide a basis for reassessment of the current TLV for n-hexane, particularly when it is used in conjunction with acetone. PUBLIC HEALTH RELEVANCE: Hexane is a very widely used chemical in industry, consumer products and gasoline that has known toxic effects, particularly on the nervous system. As hexane exposure is widespread, it is important to understand whether current permitted exposure levels are protective. This study will assess this by investigating possible effects on the nervous system, the reproductive system and the eye in a large group of auto mechanics, many of whom have been exposed to hexane in their work.